Boiler return temperature control

[Bob Rohr]

Good to draw attention to the valve flow capacity Scott.
The Caleffi 280 valve only has a 14Cv in the 1-1/4" version. Size the pump according to required flow, I'd agree a 15-58 may be on the small side.

Also pay attention to the differential of the valve. The Caleffi valve will close off the bypass 100% at temperature + 18°, So a 140° valve closes bypass completely at 158°.

I actually dropped mine down to a 115° + 18 for a 133° boiler return temperature protection.

Then issue I had with the 140° was my EKO would start ramping down before my bypass was closed 100%.

I have an early "metric" control and the temperature knob setting would not allow the boiler to go above 170F, and the blower started ramping down before that.

 

[velvetfoot]

For kicks, I bypassed around my measly 110 gal buffer tank with a motor operated valve and controller because I figured higher temperature water could get to the baseboard that way, instead of the big cool off with the buffer water. Not sure it was worth it though. With that 1000 gal tank, maybe it would be. What's nice about the motor valve is that it can be tuned. What's not nice about is that it has to be tuned. These are only my observations.

 

[maple1]

I don't think the 'thread reviver' ('New OP'?) mentioned how far away his boiler was from storage - therefore my assumption was they were next to each other. So the typical 15-58 boiler circ may cover his needs quite adequately. My unit (LK) has a 15-58 3 speed circ. It handles my 40kw boiler just fine on low speed. I tend to run things on the lower side of system temps though, so my fire is pretty well out by the time the second lap through storage is coming to an end. If I was to get into a third lap, or try to run higher supply temps - I might be looking to shift up to a higher speed. But it seems to have some flow in reserve.

 

[Elmer70]

Thanks for the insight guys. Yes maple1 my boiler is very close to my storage, about 8-10' fitting to fitting. They are both located in a boiler room inside my pool house. It is connected to my house with insulated 1-1/2" Uponor he-pex. Runs are less than 40' from pool house to house. Near boiler to storage piping will be plumbed with 1-1/2" and some 2" black steel. My boiler install is going to set a record for longest project. I purchased my boiler biomass 60 in 2008 along with some parts. Life and other priorities got in the way. I have a 3 speed TACO 0010 circ. and an 1-1/2" Danfoss mixing valve. But was under the impression these are no longer favored and that better methods have become available.

I'm am not new to this forum, I've been here at hearth.com for a long time. Perhaps before there was even a separate group known as the boiler room. I rarely post as you can see. I used to have a different username but lost it during a major web redesign "whitepine".

I think for this heating season I just want to get my boiler plumbed and my garage heated.